No oak wilt in Menahga parks, says DNR – Park Rapids Enterprise

When former Memorial Forest Park & ​​Campground manager Ralph Cox suspected oak wilt last fall, he and other city staff sought help from the Minnesota Department of Natural Resources (DNR).

This summer, the DNR sent two forest health specialists – Rachael Dube of Brainerd and Megan O’Neil of Bemidji – to take a closer look at the issue.

The good news is that they have not detected any oak wilt in Menahga.

Dube and O’Neil presented their findings to the Menahga City Council on Monday, August 26.

“We can tell many things just by looking at them,” O’Neil said.

They visited the city’s beach and campground and examined oak trees that appeared diseased.

“We decided to take samples and send them to the University of Minnesota lab,” O’Neil said.

Although no oak decay was detected during the tests, other diseases were identified.

An oak tree at Spirit Lake, for example, is suffering from anthracnose. According to O’Neil, this is a very common fungal disease that occurs especially after wet weather.

Courtesy of Rachael Dube, DNR

“We’ve seen it on oak, ash, maple and many other trees. It’s really nothing to worry about,” she said. Just rake the leaves together and dispose of them. “That’s all you have to do about it.”

They suspect that oak dieback affects a number of swamp oaks with thin crowns and dead branches at the top.

Courtesy of Megan O’Neil, DNR

Dube explained that there is a native insect that has increased in population and that, along with a native root pathogen, is responsible for severe oak dieback. “All of these things combine to cause a decline, which simply means that these trees are slowly starting to die,” she said. “The real trigger was several years of drought in a row and then very heavy rainfall.”

They said that everything else on the beach looked healthy.

A red oak tree on the campsite showed no signs of disease but is dying.

Courtesy of Rachael Dube, DNR

They suspect that a nearby RV dump station, whose drainage leads to the tree, is the cause. “We’re wondering if some people are dumping things they shouldn’t be dumping,” O’Neil said. “The other trees in the area don’t seem to be affected.”

Dube reported that there has been some decline in red oak trees at the campground, “but it is not a general concern.”

Both said they were glad they were called in to investigate, adding that there are many problems that could affect oak trees.

O’Neil noted that oak wilt is particularly problematic this year. “The list is endless,” she said. “I want you to know that our oaks are healthy and our forests are healthy. We’re dealing with all of these problems and the forest does a really good job of sustaining itself – until we get to oak wilt. That’s a big challenge.”

According to the DNR, oak wilt is a deadly disease that affects all oak species found in Minnesota. It is caused by a non-native, invasive fungus.

Red oaks die within one to two months of infection. Swamp oaks die after one to seven years.

“Oak wilt is becoming more common in the Brainerd area,” Dube said, pointing to a current map of known cases.

The DNR is finding large amounts of dead oak trees west of Baxter and east of Pillager and in scattered areas near Little Falls.

“Unfortunately, it’s creeping up on you,” she said.

Oak wilt spreads naturally in two ways: above ground through sap beetles, which deposit their spores on fresh wounds, and underground through the fused roots of different trees, so-called root grafts.

It can also be transported through firewood, O’Neil added.

Diagnosis is also very difficult, they said. They often re-examine the tree, get a second opinion and send samples to the University of Michigan Plant Disease Clinic ( https://pdc.umn.edu ).

The DNR recommends that property owners who spot oak wilt symptoms outside or within their perimeter take photos, record the location and report it using the EDDMaps app (https://apps.bugwood.org/apps/eddmaps) or the website at www.eddmaps.org.

Dube said oak wilt has been stopped from spreading to other tree species.

“We tell people: if possible, try to make your forest more diverse. That’s the best thing you can do because we expect there will be more invasive species in the future. So if you try to plant different species, you can make your forest more resilient to these problems.”

For more information, visit mndnr.gov/oakwilt.